1.0 Field of the Invention
This invention relates generally to gemstones, and more particularly to a computer-based system and method for evaluation of a gemstone by modeling light propagating through the gemstone.
2.0 Related Art
Very few subjects have plagued the diamond industry more than the subject of cut. The basis for conventional cut grading of gemstones was established in 1919 by Marcel Tolkowsky, an industrious Antwerp diamond cutter. In his mathematical dissertation entitled "Diamond Design, A Study of the Reflection and Refraction of Light in a Diamond," Tolkowsky established mathematically an optimal brilliant cut for a diamond that is still widely used today. The Tolkowsky cut defined certain dimensions (that is, table diameter, crown height and pavilion depth) of the diamond as percentages of its girdle diameter. Thus, the Tolkowsky cut is scalable, and so can be used for a different sizes of this style of cut.
Although Tolkowsky's cut represented a milestone in the industry, it is based upon a two-dimensional profile, and so does not account for three-dimensional reflective and refractive effects. Furthermore, the Tokowsky model doesn't account for differences or variations in facet types, sizes or positions, or assymetries present in some cuts.
Further, Tolkowsky apparently relied upon a single incident light ray to create the Tolkowski cut. This lighting model, therefore, has some shorfalls due to the fact that an actual gemstone is normally illuminated from a myriad of directions. Despite the shortcomings of the Tolkowsky cut, it is still in use today. Many gemstone cut grades continue to be based on deviations from the proportions of the Tolkowsky cut.